Check the caliber on the barrel rather than the receiver.
@OP
If you find an AR marked for .233 caliber, get a pic.
.223 Wylde, though, can handle both, as I understand it.
Somewhere in the mix is 5.56 Multi, too.
It means nothing.
In the imortal words of Hillary Clinton what difference does it make????
Someone please show me in the last 35 years where there has been any kind of failure in an AR type rifle.